It is a continuing problem with the use of wind-driven turbines to provide a cost-effective method of smoothing the aerodynamic torque input so as to reduce torque fluctuations in the drive train from the turbine input to the generator and to improve the quality of the electrical power output. It is particularly desirable to improve the electrical power output to such an extent that the alternating current generator can take the form of a normal "utility-grade" synchronous generator. At present, most commercial windmills use an induction generator to provide a limited slip characteristic which maintains drive-train torque fluctuations within acceptable limits. Such generators can only provide the power quality of a synchronous generator by expensive modification.
The use of a synchronous generator would be of significant benefit for windmill users. However, use of a synchronous generator requires (and use of an induction generator would benefit from) compliance to reduce the magnitude of the transfer function between the aerodynamic input torque and the drive-train torque to reduce fatigue loading on mechanical parts and to smooth the electrical power output.